The IMRT-HIT-SNT trial is a prospective, mono-centric, phase II trial evaluating toxicity and efficacy in the combined treatment with intensity-modulated radiation therapy (IMRT) and carbon ion (C12) boost. Primary endpoint is mucositis ≥ CTC°3, secondary endpoints are local control, disease-free survival, overall survival, and toxicity. Planned accrual of the trial includes 36 patients with histologically proven (≥R1-resected or inoperable) sinonasal malignancies.